Process of and apparatus for drying wet material.



W. BRATKOWSKI.

PROCESS 0F AND APPARATUS POR DRYING WET MATERIAL.

APPLICATION FILED FEB. 3,1910.

Patented Aug. 30, 1910.

laf/@bn Wpnesses W A WLADISLA'US BRATKOVQSKI, OF' BERLIN, GERMANY.

PROCESS 0F AND APPARATUS FOR DRYIN Gr WET MATERIAL.

Specication of Letters Patent.

Patented Aug. F30, 1910.

Application led February 3, 1910. Serial No. 541,847.

To all 'whom it may concern:

Be it known that I, WLADIsLAUs BRAT- KOWSKI, -a subject of the German Emperor, and residing at Berlin, Germany, have invented a certain new and useful Improved Process of and Apparatus for Drying IVe't A to flow in an exchange of heat device past of heat.

the'discharging air, ing the same to a single current of began and ended rated by walls 1n the device for exchange This arrangement had defects which did not allow of a general employthus preliminarily heatsmall extent. Only one air was employed, which ment of known devices for exchange of heat.

Namely, if the discharging air was at a low temperature, say 30 to 35 C. it was not worth while to employ an exchange of heat device, as the small difference of temperature between the entering and issuing air retarded the exchange of heat and rendered necessary a voluminous, expensive exchange of heat device for completely absorbing the heat. If, on the contrary, the discharging air was at a higher temperature, say to- C. or 60 to 80 C., it was qulte impossible to render useful the heat stored therein by employing the known process referred to because the highly heated air had, of course, to possess a less velocity of iow in orderthat it might become saturated, while large quantities of cold air were reqvuisite for cooling it. This necessarydifference in the velocity of flow at the beginnin and end of the same current of air forme an insurmountable obstacle in emplo ing exchan e of heat devices. Neverthe ess, vprecise y the high temperatures, which are absolutely necessary for rapidly completely drying many goods, do not a mit of economical operation without re-l at` opposite places sepa- A covery of the active and latent heat contained in the discharged air.

N Ow accordingto my invention I recover i the heat from the issuing air by employing two separate currents of air, one of which flows through a denite portion of the material to be dried and is heated by an exterior source of heat, as e. g. a tubular heater or the like, whereas the other current flows through another portion of the material and obtains its heat in an exchan e of heat device from the directly-heated rst current of air. The two currents of air, of which the first has just flowed through the material to be dried and is saturated with heat and moisture while the other is just entering into the machine, iow past one another in this manner separated by walls, and their temperatures are equalized, because the one loses its heat and the other takes it up.

v My process for drying various materials can be employed in manifold'ways. One

definite device does not come into question; on the contrary, all drying apparatuses employed in the art for the most various purposes can be used for carrying my process into practice.

The two currents of air may both be through currents i. e. entering into and passing out of the machine, or the directly-heated current may be employed circulating in the machine, while only the other current which cools the former passes out ofthe machine. In the former instance the directlyheated current of air flows, after passing through the heater, through a portion of the materlal to be dried and, after leaving the material, into the exchange of heat device which can be made preferably of copper or brass in the manner of a tubular heater. In this exchange of heat device the hot current of air saturated with moisture plays the same part as steam in a tubular steam heater. After leaving this exchange of heat device the cooled current of air flows into the open air. The second current of air, on'the contrary, first flows through the exchange of heat device, receives heat here from the rst current of air and enters into the drying apparatus in order to flow through another portion of the material to be dried and afterward leave the machine.

My process may suitably be modified by causing the directly-heated current of air to circulate, z'. e. not allowingit to pass into the pieces like" yarns, fruit, grain` and the like, y can be dried, and Fig. 2 shows a machine for drying textile fabrics As shown in Fig. 1, two different chambers l and 2 are employed, in which shelves 3 are so arranged that in the chamber 1 the shelves pass in upward direction according to the arrows, while in the other chamber they pass in downward direction, while the charging and emptying tallies` place at the point 31. Slides 4 may be'opened and the shelves. movedforward forf'charglng or removing, buti saidslides are `otherwise, kept closed. The heat-exchanger 5, shown 1n section, is made in the manner of the usual alrpipe heaters.y An air-heater, shown melevation, heats the air which is forced to circulate, by the ventilator 7, through the chamber 2, the suction-pipe 8 and the conducting tubes 9 and 10. Another larger ventilator 11 draws in, from the outside air, the cooling air-current whichis forced through the conducting tube 12, the heat-exchanger 5, the conducting tube 13 and the chamber l to the outside air. The operation of this form of drier 'is 'as follows: While the shelves are being periodically movedin the direction of the arrows 14:V and 15 in the chambers, the ventilator 7 `forces air from the lower part i of the chamber l2v through the heat-exchanger 5 to the suction-tube 8 and forces the same through the tube 9 to the air-heater 6 and kthroughthe tube 10 yinto the u per end of the chamber 2. The air circu ates therebyconstantly through the chamber 2, is saturated in. the latter with moisture, the larger part of which moisture leaves the airy when the air is cooled in the heat-exchan er. That is to say, theair is cooled and drled, and is then returned through the air-heater 6 so as to take up again its work of drying in the chamber 2. The cooling of the circulating air is accomplished inthe heat-exchanger 5 by the ventilator 11, which draws in cool outside air `and conducts the same through ythe tube l2 into the interior of the heatexchanger 5, where it abstracts the heat from the circulating hot air and is used in the chamber 1 for the reliminary heating ofC the substancesv to e dried. If the hot-air current is not required for circulation it is conducted through the tube 16 into the atmos here,

Fig. 2 s ows'an apparatus for drying texanother.

tile fabrics; In this apparatus the fabric enters through an opening in the upper corner of the closed casin 22, which is divided by means of alternatlng horizontal' partitions into a number of spaces through which the fabrics are drawn over guide-rollers in zigzag course, and is taken out of the apparatus at the lower'corner, as shown by the arrows in Fig. 2. The partition 231 separates the entire casing into two vseparate chambers for utilizing the double air-current employed. Through the lower chamber the hot-air current passes, while the upper chamber is supplied with a partly heated cold-air current. The ventilator 27 sucks the dried and cooled circulating air through the heat-exchanger 25 through the tube 28 and forces it through the tube 29 into the Y casing so asvto circulate in the direction opposite to the movement of the fabric to be dried. The air is gradually heated by con-` tact with the heating tubes 30 and acts at 31 on the fabric. The air isv drawn off at 32 from the casing, after it has passed in zig-l 25 and from the same through the exhaustfan 27. The ventilator 33 forces the cold air through the heat-exchanger 25 and the tube 34 to a tube 35, which is located in the casing, from which it -passes through openings in the direction of the arrows in upward direction and through the outlet 36 into the atmosphere. .In this case, instead of one circulating air-current, two air-currents can be used. 'The essential feature in this apparatus is that the hot-air current after passing through the casing kgives off its latent and sensible heat to the coolaircurrent in the heat-exchanger 25.

As already stated, the execution f my process is not bound to one definite apparathe machine, and the current of air may How 'alongone constant path; or the material mayy remain stationary and the currents of air be so directed that sometimes they How past one part vof goods and sometimes past .Whether the directly-heated or the indirectly-heated current of air is used for preliminarily drying or completely drying the goods is of no importance for the essence of my invention. In those instances when the goods are to come out of the machine completely dried, as e. g. in the' case of dried fruit and vegetables, the through current of air is preferable for complete drying and the circulating, on the contrary, for preliminary drying; in the textile and paper mdustry, however, when the goods must preferably have a certain customary degree of y moisture as they leave the machine, the revverse employment of the mentioned .currents of air'is preferable. Lastly, the circulating current of air may be made use of for evaporating the moisture from the central portion of the goods in the machine, While the through curi'ent'of air is split in the inachine into two currents and is employed both for complete and preliminary drying.

In` executingl my process the directlyheated current of air should have as high temperature as possible. The more nearly it approaches to 100o C. the more favorable is the operation of the plant. When evaporating a definite quantity of Water only a very weak current of air requires to be sent through the heater, While, on the other hand, the quantity of cold air requisite for precipitating the vapor contained in the discharged air can ow at an optional velocity through the exchange of heat device.

I claim: l. The herein described process of drying material consisting inl forcing a current of air in a cycle through the material to be dried, imparting heat to the air just before it enters the material, transferring heat from the airas it leaves the material to a second current ofair, and passing said second current through another portion of the material after the transfer.

2. In a drying apparatus the combination of means for creating two separate cur# rents of air one of which travels in a cycle, means for heating the cycle current, means for passing said currents under the conductive influence of each other, and means for subjecting the material to be dried to the action of said currents.

In testimony, that I claim the foregoing as my invention, I have signed my name in presence of tWo subscribing Witnesses.

WLADISLAUS BRATKOWSKI. Witnesses:

HENRY HASPER,

WOLDEMAR HAUPT. 

